The present invention relates to a helical-scan type digital signal recording/reproducing method for recording and/or reproducing digital data on and/or from a magnetic recording medium by using a rotatable magnetic head drum assembly and by making use of a read-after-write or RAW function for confirming the recorded state of the signal. The present invention is also concerned with a signal recording/reproducing apparatus for carrying out the method.
Of the digital signal recording apparatuses provided with a rotatable head drum assembly such as a digital video tape recorder (also referred to as the VTR in abbreviation), there exists a recording apparatus which is equipped with a read-after-write function (also referred to as the RAW function) for making it possible to confirm or verify the recorded state of a signal immediately after the recording thereof. The read-after-write function is known also as the verifying function. Incidentally, the recording apparatus imparted with the read-after-write or RAW function is disclosed, for example, in U.S. patent application Ser. No. 433,961 filed on Nov. 9, 1989 and now matured to U.S. Pat. No. 5,142,422.
In general, in the recording apparatus equipped with the RAW function such as mentioned above, an input signal is recorded with a pair of rotary heads, whereupon the input signal as recorded is instantaneously or immediately reproduced with another pair of rotary heads with a view to confirming or verifying the recorded state of the signal. In case the input signal is not recorded, appropriate measures such as repetitive recording of the same input signal may be taken.
Furthermore, there is also known such a recording apparatus in which an input signal of two or dual channels recorded with a pair of rotary heads are simultaneously reproduced on a channel-by-channel basis by means of another pair of rotary heads even when the recording apparatus is not provided with the read-after-write or RAW function.
For having better understanding of the present invention, background techniques thereof will first be described in some detail. FIG. 1 of the accompanying drawings shows, by way of example, a structure of a rotatable magnetic head drum assembly 10 employed in a recording apparatus imparted with the RAW function. Referring to the figure, a rotatable magnetic head drum assembly designated generally by reference numeral 10 includes a rotatable drum 12 provided with a pair of rotary heads (first and second rotary heads) Wa and Wb which are mounted on the outer periphery surface of the rotatable drum 12 with a predetermined angular space .DELTA.L therebetween as viewed in the rotating direction Dr of the rotatable drum 12, wherein the rotary heads Wa and Wb are positioned adjacent to each other in a direction orthogonal to the rotating direction Dr, as can be clearly seen in FIG. 2A. Furthermore, another pair of rotary magnetic heads, i.e., a third rotary head Ra and a fourth rotary head Rb, are mounted on the rotatable drum 12 substantially in diametrical opposition to the pair of the rotary heads Wa and Wb (i.e., with an angular space of ca. 180.degree. relative to the heads Wa and Wb), wherein the third and fourth rotary heads Ra and Rb are disposed with an angular space .DELTA.L therebetween in the rotating direction Dr of the rotatable drum 12 and adjacent to each other in the direction normal to the rotating direction Dr, as can be clearly seen in FIG. 2B. When the first and second rotary heads Wa and Wb are operated as the recording or write heads, respectively, the third and fourth rotary heads Ra and Rb then serve as the reproducing or read heads for confirming or verifying the signal state recorded by the heads Wa and Wb. Of course, the third and fourth rotary heads Ra and Rb can operate also as the ordinary reproducing heads, respectively.
In the signal recording operation mode, a magnetic tape 14 is helically wound on and around the rotatable drum 12 over an angular span of ca. 180.degree., and record tracks Ta and Tb are generated sequentially in a helical pattern without intervening guard bands by means of the first rotary head Wa and the second rotary head Wb mentioned above, as is illustrated in FIG. 3. Parenthetically, in FIG. 3, reference symbol Dt designates a transporting or feeding direction of the magnetic tape 14 and Ds designates a scanning direction of the magnetic heads. In the rotatable magnetic head drum assembly 10, the mounting positions of the four rotary heads Wa; Wb and Ra; Rb on the rotatable drum 12 (or offsets between these heads) are so selected or determined that a pair of tracks i.e., the first track Ta and the second track Tb formed by the first and second rotary heads (recording heads) Wa and Wb can be scanned, respectively, by the third and fourth rotary heads (reproducing heads) Ra and Rb immediately in succession to the recording operation.
In the rotatable drum 12 constituting a main body of the rotatable magnetic head drum assembly 10, a rotary transformer is ordinarily provided as a means for transmitting the input signal to be recorded to the recording or write heads (first and second rotary heads) while transmitting the signal reproduced by the reproducing or read heads (third and fourth rotary heads) to an external signal processing circuitry.
FIG. 4 of the accompanying drawings shows schematically an exemplary arrangement of such rotary transformer. The rotatable drum 12 shown in FIG. 4 is composed of a stationary drum half 12a and a rotatable drum half 12b, wherein the rotary heads Wa; Wb and Ra; Rb are mounted on the rotatable drum half 12b in the manner described above. A rotary transformer denoted generally by reference numeral 16 is disposed along a plane across which the stationary drum half 12a and the rotatable drum half 12b are disposed in opposition to each other.
In the case of the rotatable magnetic head drum assembly 10 illustrated in FIG. 4, there are formed in each of the stationary drum half 12a and the rotatable drum half 12b four recesses in a coaxial circular pattern around a rotating shaft of the rotatable drum 12, wherein four coils 18a; 18b and 20a; 20b are fixedly fit in these recesses, respectively. With the structure of the rotary transformer 16 shown in FIG. 4, the coils 18a and 18b may be used as a rotary transformer coil assembly for transmitting a recording signal from the stationary drum half 12a toward the rotatable drum half 12b while the other coils 20a and 20b may be used as the rotary transformer coil assembly for transmitting a reproduced signal from the rotatable drum half 12b toward the stationary drum half 12a.
At this juncture, it should be recalled that when the first and second rotary heads Wa and Wb are mounted on the rotatable drum 12 with the angular space .DELTA.L therebetween as viewed in the rotating direction of the drum 12, the third and fourth rotary heads Ra and Rb are equally mounted on the rotatable drum 12 with the same angular space .DELTA.L therebetween, as described hereinbefore by reference to FIGS. 2A and 2B. With the rotatable magnetic head drum assembly 10 of such structure, the input signal of the first channel is recorded and reproduced by means of the first rotary head Wa ad the third rotary head Ra, respectively, while the input signal of the second channel is recorded and reproduced by the second rotary head Wb and the fourth rotary head Rb, respectively. Furthermore, the first and third rotary heads on one hand and the second and fourth rotary heads are angularly distanced by ca. 180.degree.. Consequently, there applies valid between the write or recording periods and read or reproducing periods of the aforementioned four rotary heads such relations as illustrated in FIGS. 5A and 5B, being developed in the drum rotating direction.
In conjunction with the developed views illustrated in FIGS. 5A and 5B, it should be recalled that the rotary heads Wa and Ra are positioned, being angularly distanced from each other by 180.degree., with the rotary heads Wb and Rb being also angularly distanced by 180.degree., and that the rotary heads Wa and Wb are mounted with the angular space .DELTA.L therebetween with the rotary heads Ra and Rb being mutually distanced for the same space .DELTA.L. In the verification or confirmation mode, the recording operation and the reproducing or read operation (the data verifying operation, to say another way) are repeated alternately for one and the same channel.